MYODOME AND TRIGEMINO-FACIALIS CHAMBER 233 
rupted, either anterior or posterior to the branch sent out with 
the nervus opticus, as it is in Hyodon, while a branch, not found 
in either Hyodon or Scorpaena, is sent outward, anterior to the 
nervus opticus, to join a branch of the orbitonasal artery and 
then go to the eyeball. 
In a 63-mm. specimen of Trigla hirundo the conditions dif- 
fer in that the depression in the dura mater which lodges the 
hypophysis has a relatively wide and flat floor from which three 
membranes arise, one median and one at each lateral edge of 
the floor. These membranes are each inserted on a correspond- 
ing ridge on the dorsal surface of the parasphenoid, and the 
space enclosed, on either side, between them and the para- 
sphenoid, lodges the rectus internus. Thus the ventral com- 
partment of the myodome here rises to the ventral surface of 
the pituitary depression, and hence lies between right and left 
halves of the dorsal compartment. This condition continues 
posterior to the hypophysis for a certain distance, the roof of 
the ventral compartment of the mycdome there forming the 
median portion of the floor of the cavum cerebrale crani; but 
at the membranous anterior edge of the prootic bridge, the roof 
of the compartment begins to recede from the floor of the cavum 
cerebrale cranii, and, the lateral halves of the dorsal compart- 
ment uniting with each other above it, the conditions become 
as in Scorpaena. Apparently because of this intercalation of 
the ventral compartment between the anterior ends of the 
dorsal compartment, the pituitary veins are greatly reduced, 
the hypophysis being drained in part by the encephalic veins. 
In this embryo of Trigla the nervus palatinus facialis per- 
forates the floor of the pars jugularis of the trigemino-facialis 
chamber and enters the dorsal compartment of the myodome, 
this apparently being as I found this nerve in the adult Secomber. 
In the adult Cottus octodecimospinosus I found (Allis, ’09) 
the myodome continued posteriorly a short distance in the 
basioccipital, and not opening posteriorly on the ventral sur- 
face of the cranium. The prootics have perfectly normal hori- 
zontal processes, and they are shown, in my figures, preformed 
in cartilage and forming the roof of the myodome. ‘The para- 
sphenoid has diverging hind ends. 
